The invention relates to a switch-disconnector control unit. A switch-disconnector is used to form a safe clearance between an electric circuit to be disconnected and other electric circuits, or it is used to de-energize a part of the electric circuit in order to assure the safety of the work.
Switch-disconnectors are used in electricity distribution networks. A switch-disconnector is used to form a safe clearance between an electric circuit to be disconnected and other electric circuits, or it is used to de-energize a part of the electric circuit in order to assure the safety of the work. For this purpose, the switch-connector is arranged to be controlled between three switching positions. These positions are: disconnector closed, disconnector open and disconnector earthed. In the close position, the disconnector connects an electric circuit disconnected by means of said disconnector to another electric circuit. In the open position, the disconnector disconnects the electric circuit disconnected using said disconnector from another electric circuit. In the earthed position, the disconnector earths the electric circuit disconnected using said disconnector to be de-energized in order to assure the safety of the work.
Manually operated switch-disconnector control units are previously known in the art that are controlled using a crank connected to the control shaft of the disconnector. This requires the presence of a physical person to control the procedure, who carries out the control in the immediate vicinity of the switch-disconnector. It is also known to use remote-controlled control units provided with a motorized actuator that can be controlled either manually or using remote control for controlling the disconnector. These disconnector control units comprise a spring actuator connected to the control shaft of the disconnector. The spring in the spring actuator is tightened using a motorized actuator. When the motorized actuator has rotated the control shaft to the tripping point of the spring, the spring trips and provides an adequate amount of strength to open or close the contact of the switch-disconnector.
Control units for bistable switch-disconnectors are also previously known in the art. In such a case, the positions concerned are close and open. Newer types of switch-disconnectors also comprise an earth switch integrated to the switch-disconnector and a spring actuator. Thus, the spring actuator comprises three positions: open, close and earthed. The spring actuator may alternatively be provided with two control shafts or two control points in order to switch said actuator between the open and close positions and between the open and earthed positions. Such a conventional switch-disconnector provided with an earth switch comprises a manual control unit and a motor-operated control unit, which opens and closes the main circuit of the switch-disconnector. Said switch-disconnector further comprises a separate manually operated control unit, which opens and closes a separate or integrated earth switch. In addition, one or more very complicated blocking mechanisms are required to prevent malfunctions, such as the simultaneous closing of the switch-disconnector and the earth switch. The structure of such a switch-disconnector control unit is very complex and liable to malfunction, as it comprises a plurality of separate structural parts, wherefore it is also expensive to implement.
A general requirement for a switch-disconnector is that switching between open and earthed positions can only be carried out manually and the switching between open and closed positions can be performed both manually and using remote-control.
Significant drawbacks are thus associated with the prior art. The prior art switch-disconnector control units described above are manually operated or motor-operated if they are remote controlled, whereby the structures thereof are complicated and liable to malfunction and as regards the switching speed very slow. What is also essential is that remote control to the earthed position is prevented, which requires very complex blocking mechanisms in the prior art solutions.
It is an object of the present invention to eliminate the drawbacks of the prior art and to provide an improved solution for a switch-disconnector control unit and to provide a switch-disconnector control unit comprising a single control shaft that enables to switch the switch-disconnector between the open and close (OPEN-CLOSE) positions and between the open and earthed (OPEN-EARTHED) positions. Switching between the open and close positions (OPEN-CLOSE) is carried out manually by turning the control crank connected to the control shaft of the disconnector or by means of remote control (an automatic actuator) by turning the control shaft of the disconnector. Switching between the open and earthed positions (OPEN-EARTHED) can only be carried out manually by turning the control crank of the disconnector. In addition the control motion provided by the remote-controlled actuator between the open and close positions (OPEN-CLOSE) and vice versa is fast and strong, but the actuator does not, however, prevent the manual control of the switch-disconnector.
This is achieved with a switch-disconnector control unit provided with the characteristics defined in the claims in accordance with this invention. The switch-disconnector control unit comprises an actuator including a moving control member and a spring actuator including a control shaft, whereby the control member is connected from the first end thereof to the actuator and from the second end thereof to the control shaft of the spring actuator, whereby the control shaft is arranged to control the contacts of the switch-disconnector using the spring actuator, and the invention is characterized in that the control member comprises a connection element, which connection element is jointedly connected from the first end thereof to the control shaft through a control member, and from the second end thereof the connection element is jointedly connected to the control member of the actuator, and an articulated joint at the second end of the connection element is substantially formed of an opening parallel to the control shaft in the vicinity of the end of the connection element and of a pin parallel to the control shaft connected to the control member of the actuator substantially in the vicinity of the end of the connection element side thereof, the pin being arranged to the opening, which is dimensioned to be large in relation to the pin.
In other words, the actuator in the control unit comprises an electromagnet, the armature of which linearly moves the control arm, which is connected from the first end thereof to the control shaft controlling the contacts of the switch-disconnector using the spring actuator through the control member and from the second end thereof to the armature of the electromagnet. The control member comprises a connection element, which is jointedly connected from the first end thereof to the control shaft and from the second end thereof jointedly connected to an arm part connected to the armature of the electromagnet. The articulated joint at the second end of the connection element, or at the armature end, is substantially formed of a preferably oval opening parallel to the control shaft the end of the connection element and of a pin parallel to the control shaft connected to the arm part in the vicinity of the to the control shaft connected to the arm part in the vicinity of the end of the connection element thereof, and said arm part being connected to the armature of the electromagnet, and the pin is arranged to said oval opening.
The preferred embodiments of the invention are disclosed in the dependent claims.
In the solution of the invention the oval opening at the end of the actuator in the connection element connected to the control member moving the control shaft preferably resembles an ellipse in the longitudinal direction of the connection element. The opening is dimensioned to form a clearance in the joint between the connection element and the control member of the actuator. Such a connecting way that allows a particular clearance in the joint allows turning the control shaft of the disconnector manually into a position, where the control member controlling the control shaft to which the connection element is jointedly connected, can revolve over the dead centre thereof to the other side of the control shaft and further to such a point where the switch into the earthed position occurs. When placed into the earthed position, the actuator cannot turn the control shaft so that the disconnector is able to be directed back over the dead centre to the open position using the remote-control of the actuator, whereby such an advantage is achieved that the remote-controlled malfunctions cannot occur and the safety of the disconnector improves. Switching from the earthed position to the open position must therefore be carried out manually.
In accordance with a preferred embodiment, the articulated joint at the end of the connection element on the side of the spring actuator is substantially formed of an opening in the vicinity of the end of the connection element and of a pin parallel to the control shaft connected to the control member of the control shaft in the spring actuator, the pin being arranged into the opening, which is dimensioned to be large in relation to the pin. The shape of the opening is preferably oval.
The actuator controlling the disconnector is preferably an electromagnet, the armature of which controls the control member, which moves the control shaft of the disconnector. The electromagnet is double-acting, meaning that the armature thereof moves linearly back and forth by means of the electric control. Consequently the electromagnet is able to direct the disconnector to both the open and close positions. The control shaft of the disconnector control unit is arranged to control the contacts of the switch-disconnector through the spring actuator. This spring actuator comprises one or more springs to be tightened using the motion of the electromagnet armature, in which case the spring of the spring actuator trips substantially at the end point of the armature motion, thus opening or closing the contacts of the switch-disconnector.
The disconnector control unit according to the invention, in which an electromagnet functions as the actuator, is capable of controlling the disconnector by means of remote control in the same way as the motorized actuator and also allows controlling the disconnector manually. In comparison with the motorized actuator the electromagnet actuator provides such an advantage that the structure of the electromagnet actuator is significantly simpler and it performs the control operations and sequences considerably faster than the motorized actuator. The magnet actuator also provides such an advantage that the electromagnet armature moves quite freely, while the electromagnet coils are de-energized, without hindering the manual control of the disconnector. Furthermore, the strength curve of the electromagnet actuator is highly suitable to tighten the springs of the spring actuator, since the strength increases towards the end part of the armature motion as the strength required for tuning the spring.
Moreover, in comparison with the previously known disconnector control units provided with magnet actuators, in the double-acting switch-disconnector said magnet control unit can be connected to the switch-disconnector, whereby the mechanism of the invention allows switching the disconnector to all three positions, i.e. open, close and earthed, as required.
The solution of the invention thus provides the following significant advantages:
1. The switching of the switch-disconnector to open and close positions (OPEN-CLOSE) can be carried out both automatically using electrical control and manually.
2. The length of stroke and the strength curve of the electromagnet can preferably and efficiently be utilized.
3. The switch between the open and earthed positions in the switch-disconnector can only be carried out manually. Even though the control voltage of the magnet actuator is switched in the earthed position, the magnet actuator provided with the mechanism of the invention cannot direct the disconnector from the earthed position and no separate protection mechanisms are required, and no mechanical disconnection mechanism is required between the control shaft and the electromagnet armature for opening and closing the earthed position.